The field of the present invention is lash adjusters for engines and particularly for the valve train thereof.
Lash adjusters of the disclosed type are known to employ a cylinder, closed at one end, in which a plunger is slidably arranged. A compression chamber is defined at the closed end of the chamber where a spring biases the plunger towards the open end of the cylinder. A passage is known to be formed through the plunger which passage is controlled at one end by a one-way valve and is permanently closed off at the other end. Side passages extend to an annular reserve chamber defined by a diaphragm sealed at a first end to the plunger and at a second end to the cylinder.
It has been the practice to insert a hard ball into the passage for closure of the one end. The ball has been mechanically driven into an interference fit to form an appropriate seal. One problem associated with this is that the hard material of the ball at its initial insertion and thereafter may act to cause failure. This can occur as the result of stress concentrations in fabrication. The end result may be a seal failure or the introduction of metal powder into the mechanism which otherwise eventually will result in failure as well.
The area available in engines for valve mechanisms is generally at a premium. Heretofore, a substantial amount of room has been necessary for location of the annular reservoir of the hydraulic lash adjuster. This room extends the axial length of the overall adjuster even though there is no specific need for the added length for purposes of the adjuster stroke. The area needed for the reservoir is taken up by both the annular diaphragm and by extensions of the retainers located at either end thereof.